1. Field of the Invention
The present invention relates to an adaptor which is attached to a small diameter film patrone (i.e., film cartridge or magazine) whose diameter is smaller than that of a patrone chamber of a camera.
2. Description of Related Art
To miniaturize a camera, it is theoretically possible to use a small diameter film patrone whose diameter is smaller than that of the conventional JIS 135 type patrone.
To load such a small diameter film patrone in a conventional camera or developer (i.e., film developing machine) designed for the JIS 135 type patrone, it is necessary to use an adaptor which compensates for the difference in diameter between the small diameter patrone and the JIS 135 type patrone.
Some photographers may use the small diameter patrone only, while others may alternately use the small diameter patrone and the JIS 135 type patrone for the same camera. In the case that only the small diameter patrone is used, the adaptor can be permanently incorporated in the patrone chamber of the camera.
On the other hand, in the case that the small diameter patrone and the JIS 135 type patrone are alternately used, the adaptor is attached to the small diameter patrone when the small diameter patrone is to be used, so that the adaptor together with the small diameter patrone can be accommodated in the patrone chamber of the camera.
In the first case mentioned above, it is necessary to prevent the adaptor from accidentally coming out of the patrone chamber. The same is also true when the small diameter patrone is used in a conventional developer for the JIS 135 type patrone. In the second case, it is necessary to prevent the small diameter patrone from being easily detached from the adaptor.
The JIS 135 type patrone is provided on the outer peripheral surface thereof with a film information indicating portion, represented by printed letters, such as film sensitivity data or the number of frames of the film loaded in the patrone. A similar information indicating portion may be provided on the outer peripheral surface of the small diameter patrone.
A camera is also known which is designed for the JIS 135 type patrone, in which the back cover of the camera is provided with a transparent information indicating window, so that the information of the indicating portion of the JIS 135 type patrone loaded in the patrone chamber can be viewed from the outside of the camera when the back cover is closed.
Accordingly, in the case where the small diameter patrone is loaded in the patrone chamber of a camera having an information window on the back cover, it would be convenient if the information of the indicating portion of the small diameter patrone could be viewed through the information indicating window after the back cover is closed.
However, if the adaptor, which compensates for the diameter difference between the small diameter patrone and the JIS 135 type patrone, is provided between the small diameter patrone and the patrone chamber of the camera, information regarding the small diameter patrone will not be visible from the outside of the camera, since the small diameter patrone will be substantially enclosed in the adaptor.
In a known camera, a film guide adjacent to an open inlet of the patrone chamber of the camera is provided to guide the film withdrawn from the patrone. Particularly, in a conventional camera which uses the JIS 135 type patrone, when the patrone is loaded in the patrone chamber of the camera, it is positioned so that a film outlet of the JIS 135 type patrone is oriented toward an extension of the film guide.
Consequently, when the JIS 135 type patrone is loaded in the patrone chamber of the conventional camera designed for the JIS 135 type patrone, the film withdrawn from the patrone through the film outlet thereof can be stably advanced, i.e., the film can be fed without becoming misaligned or bent. Stable advancement of the film not only contributes to a reduction of the winding or rewinding force of the film, but also protects the film surface from being damaged.
However, if the small diameter patrone housed in the adaptor is loaded in the patrone chamber of the conventional camera designed to receive the JIS 135 type patrone, the film outlet of the small diameter patrone will not align with the film outlet of the JIS 135 type patrone in the patrone chamber, since a rewinding fork projecting into the patrone chamber is located at a fixed position.
To this end, when the small diameter patrone housed in the adaptor is loaded in the patrone chamber of the conventional camera which uses the JIS 135 type patrone, it is necessary to prevent the film withdrawn from the small diameter patrone from winding or being bent.
In a known camera, film guide projections are provided along a passage of the film withdrawn from the patrone and wound onto a winding spool to prevent the film surface from being damaged and to retain the flatness of the film. The film guide projections come into contact with the portion of the film other than the picture plane on opposite sides of the film during the passage of the film on the guide projections. Since the picture plane of the film does not come into contact with the guide projections, the picture plane can be prevented from being damaged.
To this end, when the small diameter patrone is loaded in the patrone chamber of the camera, using the adaptor, it is necessary to space the picture plane portion of the film, withdrawn from the small diameter patrone, from the adaptor.
Some photographers may use the small diameter patrone only. In such a case, the adaptor for the small diameter patrone can be conveniently and permanently fitted in the patrone chamber of the camera. With this arrangement, the small diameter patrone can be inserted in the permanent adaptor.
To this end, it is necessary to provide an opening on the adaptor through which the small diameter patrone can be inserted.
However, in the case that the small diameter patrone is accommodated in the patrone chamber of a conventional camera designed for the JIS 135 type patrone, using the adaptor having the insertion opening, a gap exists between the outer peripheral surface of the small diameter patrone and the back cover provided on the camera to open and close the patrone chamber in the vicinity of the insertion opening of the adaptor, since the position of the rewinding fork projecting into the patrone chamber is fixed. Consequently, the small diameter patrone can be easily and accidentally detached and drop from the adaptor.
The JIS 135 type patrone is usually provided, on the outer peripheral surface thereof, with a film information contact portion including conductor portions and insulating portions.
The patrone chamber of the camera is provided, on the inner wall surface thereof, with a film information contact portion including a plurality of contacts which can be connected to the film information contact portion of the JIS 135 type patrone.
When the JIS 135 type patrone is received in the patrone compartment of the camera, the film information contact portion of the patrone is connected to the film information terminal portion of the patrone chamber to establish an electrical connection between the terminals of the film information terminal portion which are connected to the conductor portions of the film contact information portion. Accordingly, film information, such as film sensitivity (i.e., film-speed) of film contained in the JIS 135 type patrone, which is received in the patrone chamber, can be automatically detected on the camera body side in accordance with the conductor pattern.
To this end, it is necessary to provide a film information contact portion on the outer peripheral surface of the small diameter patrone, similar to the JIS 135 type patrone, so that when the small diameter patrone is loaded in the patrone chamber using the adaptor, film information can be automatically detected.
However, when the small diameter patrone is loaded in the patrone chamber of a camera designed for the JIS 135 type patrone, using the adaptor, a gap corresponding to a difference in diameter between the JIS 135 type patrone and the small diameter patrone exists between the outer peripheral surface of the small diameter patrone and the inner wall surface of the patrone chamber, since the rewinding fork provided in the patrone chamber is located at a fixed position.
Consequently, even if the film information contact portion is provided on the outer peripheral surface of the small diameter patrone, similar to the JIS 135 type patrone, the film information contact portion does not contact the film information terminal portion of the patrone chamber. Moreover, since the adaptor is located between the film information contact portion of the small diameter patrone and the film information terminal portion of the patrone chamber, film information of the small diameter patrone, such as film-speed, etc., cannot be automatically detected by the camera body side.
When the small diameter patrone is received in the patrone chamber of a camera designed for the JIS 135 type patrone, a gap, which exists between the outer peripheral surface of the small diameter patrone and the inner wall surface of the patrone chamber, makes it impossible to stably hold the small diameter patrone in the patrone chamber while engaging the winding shaft of the small diameter patrone with the rewinding fork of the patrone chamber.
In addition to the foregoing, since the position of the film outlet of the small diameter patrone is not identical to that of the film outlet of the JIS 135 type patrone in the patrone chamber, a winding or bending of the film drawn from the small diameter patrone towards the winding spool takes place, thus resulting in an increase of the winding or rewinding force of the film or damage to the film surface.